US
Repeaters.Com
offers Uptodate Repeater Information for Ham Radio Operators. Updated
Daily from Submissions sent in by Ham Radio Operators, verified by
frequency cordinators. We also do a schedule yearly overhaul of the
Repeater List.

VISUAL DISTANCE. A rough rule of thumb is to take the square
root of the height in feet and that will give the miles from the antenna to the
ground. Repeat for the other antenna and add the number of miles. This can
be multiplied by about 1.2 to 1.3 for radio waves. For example if the
transmitter antenna is 625 feet high and the receiving antenna is 16 feet high,
square root of 625 = 25 miles, square root 16 = 4 miles. Add 25+4 = 29
miles for the visual distance. Then multiply this by 1.3 to get 37.7
miles of radio range. This gives the visual distance. And of course, transmitter
power and antenna gain, receiver noise figure and antenna gain enter into it,
see links above.

With reference to 144 MHz and 440 etc. Path loss in free space
is independent of frequency. The free space loss equation has a frequency
quantity in it to offset the loss of signal received by an isotropic
antenna. An isotropic antenna or a dipole for that matter intercepts 6dB
less wavefront energy when the frequency is doubled. There was no
increase in path loss. (In free space). Since by definition, all
isotropic antennas radiate equally well at all frequencies, there is no need
to "crank in" another 6dB to adjust for the transmit antenna when we
double the transmit frequency. I have seen that equation referred to as Path
Loss between isotropics. That describes it quite well. Most of my work is in
the GHz range so I use 96.6+ 20logF (GHz) +20 LogD (Miles).
73, Larry Wheeler

Another rule of thumb is doubling antenna elevation at VHF produces about 6 dB
gain.

Simplex --http://perso.club-internet.fr/f1orl/program/simplex.zip This software is intended to replace the
hardware logic of repeaters. With SIMPLEX, repeaters may be quickly
implemented with a few connections between the computer sound card and the
audio receiver output and microphone transmitter input.It handles simplex repeater, duplex repeater, transponder and mixed mode.
It supports classical 1750 Hz tone detection or CCTSS detection to open. It
plays any audio service message (beacon, welcome, goodbye, transmit, timerout
messages).It repeats communications either on audio detection (vox mode) or
carrier detection (if a squelch signal is available).It detects DTMF codes for
remote control.It works also as a simple parrot or voice recorder. It runs
under Win95/98/NT/2000/XP.

OFFSETS AND TONES

The
standard offsets for HF/VHF/UHF/SHF are:

29 MHz 100 kHz
(-)

147 MHz
600 kHz (+)

1.2 GHz 12 MHz (-)

50 MHz 500 kHz (-)

222 MHz 1.6 MHz (-)

2.4 GHz 20
MHz (-)

145 MHz
600 kHz (-)

440 MHz 5.0 MHz (-) **

146 MHz
600 kHz (+ or -)

900 MHz 25.0 MHz (-)

** Plus Offset In Some areas - notably Northern California.

When a repeater receives below the
transmit frequency it is termed a minus offset. A repeater that transmits on
147.13 MHz and receives on 147.73 has a plus offset. Repeater input frequencies are given as
either + or - signs to indicate whether the user's transmit frequency is above
or below the repeater transmit frequency.
Repeaters that have outputs in the lower part of
the 146 MHz portion are often plus offsets while those operating in the upper
portion of 146 MHz are minus offsets. See your repeater guides. Most of the new
rigs default to the accepted offsets.

There are now nearly 1600+ repeaters around the world connected by the internet through the internet radio
linking project (IRLP) 24 hours per day 7 days a week. The most remote repeater on the system is on
Antarctica. To call a repeater on the system you just dial a 4 digit DTMF code.